1. Technical Field
This invention relates to internal combustion engines and, more particularly, to a multi-fuel two-cycle engine employing structural fiber reinforced ceramic matrix composite (FRCMC) internal components that decrease the heat loss during the combustion process and increase the overall efficiency of the engine. The increases in efficiency result in increased power output, decreased fuel consumption, and reduced polluting exhaust emissions. It also relates to methods of making fiber reinforced ceramic matrix composite materials which are breakage resistant and highly suitable for use in the construction of components employed in a high temperature internal combustion engine.
2. Background Art
The operation of a typical prior art four-cycle internal combustion engine is shown in FIGS. 1 through 4. There are one or more pistons 10 moving up and down within a cylinder 12. The pistons 10 are connected by a connecting rod 14 to an offset crankshaft 16 which rotates in response to the up and down motion of the piston(s) 10. Most engines for automobile use have four, six, or eight cylinders. In the past, there have been automobiles with twelve and sixteen cylinders and at least one Japanese auto maker is presently selling a three cylinder engine car.
In the typical prior art four-cycle engine as depicted in FIGS. 1-4, there is an oil sump 18 which contains a quantity of lubricating oil. The oil bathes the crankshaft 16, splashes up on the sidewalls of the cylinder 12, and is positively pumped through the engine to lubricate other moving parts to reduce friction, heating, and wear. There is also a cylinder head covering the top of the cylinder 12. The cylinder head 20 and engine block containing the cylinder(s) 12 are typically water-cooled to protect metal components which will erode or even melt if temperatures are allowed to get too high. The hot water produced typically provides a heat source for heating the automobile in the winter months in colder climates.
The cylinder head 20 for each cylinder 12 contains an intake valve 22 connected to an intake manifold 24 and an exhaust valve 26 connected to an exhaust 28. Air and fuel in a vaporized form 30 are introduced into the intake manifold with a carburetor, fuel injector system, or the like. When the intake valve 22 is opened during the down-stroke of the piston 10 as depicted in FIG. 1, the partial vacuum created draws the air/fuel mixture 30 into the combustion chamber of the cylinder 12 between the piston 10 and the cylinder head 20. At or near the bottom of the piston stroke, the intake valve 22 is closed and the air/fuel mixture is compressed by the piston 10 moving upward as depicted in FIG. 2. Near the top of the compression stroke, a spark plug 32 in the cylinder head 20 is discharged with a high voltage spark to ignite the compressed air/fuel mixture and cause it to burn and impart its energy to the piston 10 in its downward power stroke as depicted in FIG. 3. The exhaust valve 26 is then opened so that the burned exhaust gases 34 are forced out the exhaust manifold 28 by the upward movement of the piston 10 as depicted in FIG. 4.
If the four-cycle engine of FIGS. 1-4 could operate under ideal conditions (i.e. a theoretical thermodynamic cycle), all the energy of the air/fuel mixture would be transferred to the piston in the form of work. Unfortunately, the conditions are not ideal due to material limitations (melting point of metal, thermal expansion, etc.), mechanical limitations (fixed valve and crank timing, friction, assembly tolerances), and energy lost to the cooling system. If the temperature of the combustion chamber could be raised by reducing the heat lost to the cooling system (adiabatic engine), the inefficiencies could be reduced. However, because of the water cooling system and the potential friction and thermal expansion problems associated with the higher temperature pistons, the internal temperatures cannot be high enough.
A supercharger or turbocharger can be added to inject the air/fuel under pressure. This can be used to force more fuel and air into the combustion chamber which results in more energy (higher temperatures and pressures) for a given displacement engine. In any event, however, the engine will typically run hotter and have a reduced life. Thus, a supercharger or turbocharger is more likely to be employed to increase engine performance rather than fuel efficiency.
Since the engine does not operate at peak theoretical efficiency, there are pollutants which must be removed to produce emissions which meet required (i.e., government regulated) standards. Typically, the pollutants are removed by a separate catalytic converter (not shown) placed down stream from the exhaust valve 26 in the exhaust system following the exhaust manifold 28.
In a typical two-cycle engine as depicted in FIGS. 5 through 7, a mixture of air/fuel/oil 36 enters the crankcase 101 via a port 103 with a one-way valve 105. The pressure differential created by the upward (compression 36) stroke of the piston 10 draws the mixture in. As the piston 10 approaches top dead center, the mixture in the cylinder 12 is ignited by a spark plug 32 thus creating an increase in pressure from the combustion process. This pressure rise forces the piston downward (power stroke) which in turn introduces positive work into the crank shaft 16 via the piston connecting rod 14. As the piston approaches bottom dead center, it travels past and thereby opens the exhaust port 28 in the cylinder wall 12, which allows the products of combustion to exit. Shortly after the exhaust port opens, the piston passes by, thus opening, the cylinder 12 intake port 24. As the port opens, a fresh charge of fuel air mixture is forced into the cylinder 12 from the crankcase by the pressure differential created in the crankcase from downward travel of the piston 10. The process then repeats providing one power stroke every revolution of the crank, unlike it's four stroke counterpart. Since there is no sump and circulating oil as in the four-cycle engine, the lubricating oil must be mixed with the fuel or be separately injected into the mixture 36, which makes the cost of operation higher and increases the exhaust emissions. In addition, the inherent intake/exhaust porting of the two-stoke engine dictates that both the intake and exhaust ports must be open for some duration at the same time, thereby allowing a portion of the raw fuel/air mixture to flow directly out the exhaust, which dramatically increases hydrocarbon emissions and decreases fuel efficiency. The inherent nature of the two-cycle design provides for minimal moving parts (thereby resulting in reduced manufacture ring costs), high specific power, and high hydrocarbon emissions. Therefore, their practical and accepted use tends to be in products such as small utility engines (lawn and garden equipment), lightweight (typically off-road) motorcycles, outboard marine engines, and the like. As mentioned in passing above, heat, friction, and metal deterioration are problems of internal combustion engines that must be factored into engine design. The more efficient the burn, the hotter the internal temperatures generated. In the prior art attempts have been made to coat critical metal parts with ceramic material in an effort to make them more resistant to heat deterioration and to improve the heat retention of the engine. For example, heat and its effects are much more important to consider with newer engines having cylinders and pistons formed of aluminum than older engines employing cast iron. The so called "aluminum engines" offer many benefits, but heat resistance is not one of them.
As shown in FIG. 8, it is known to use a monolithic ceramic sleeve 38 to line the walls of the cylinder 12 and the inside of the cylinder head 20 with a monolithic ceramic liner 40 in an alcohol fueled two-stroke engine.
The inside of exhaust manifolds 28 have also had a ceramic liner 40 applied thereto in the prior art, as depicted in FIG. 9, as there is a tendency for hot exhaust gases to generate excessive heat in areas where their path bends. Such "hot spots" can burn through or melt the metal or cause it to change physical structure to the point that there is a hole formed requiring replacement of the entire manifold. Pistons can literally have holes burned through their top 41 at the fuel ignition point. To counteract this, the prior art suggests having a monolithic ceramic liner or insert 40 in the center of the piston 10 as depicted in FIGS. 10 and 11.
Nowhere in the prior art known to the applicants herein is a structural fiber reinforced ceramic matrix composite (FRCMC) material employed for engine parts in sliding contact with one another.
Nowhere in the prior art known to the applicants herein is a structural FRCMC employed for an entire engine part.
Wherefore, it is an object of the present invention to provide a practical automobile internal combustion engine that is simple in operation and cost competitive to manufacture.
It is still another object of the present invention to provide a two-cycle automobile internal combustion engine that has high fuel efficiency.
It is yet another object of the present invention to provide a two-cycle automobile internal combustion engine that has low pollutant production.
It is a further object of the present invention to provide a two-cycle automobile internal combustion engine employing an all FRCMC combustion chamber dome, cylinder(s) and piston(s), and which can be fueled by gasoline, diesel or alcohol fuels.
It is a still further object of the present invention to provide an automobile internal combustion engine employing FRCMC parts in sliding contact with one another (e.g., sleeve and piston).
It is a yet further object of the present invention to provide structural FRCMC materials and methods of manufacture which are breakage resistant and highly suitable for use in the construction of components used in a high temperature internal combustion engine.
Other objects and benefits of this invention will become apparent from the description which follows hereinafter when read in conjunction with the drawing figures which accompany it.